Inherited Disorders and Birth Defects

Balanced translocation 7/12

10/24/2006

Question:

My son has a balanced translocation of the 7 and 12 chromsomes. We`ve seen a genetic specialist, and have been told there is no other reported case in the world. We were wondering if this is true and where we could get help with him.

Answer:

As you probably are aware, chromosomal translocations can be somewhat tricky to understand. A balanced translocation occurs when two pieces of chromosomes break off and switch places with each other. If all the chromosomal material is present, just rearranged – that is, switched places (translocated) - this person should have no health problems since all the chromosomal material needed is present and functioning properly. This is called a balanced translocation. There is no way to tell whether or not a person has one of these rearrangements unless you look at his or her blood to examine the chromosomes.

However, there can be problems if some of the chromosomal material that was switched is lost or duplicated when the chromosomes broke and the switch took place – then there is extra and / or missing information that can lead to birth defects and cognitive problems such as mental retardation. This is an unbalanced translocation.

The specific types of problems or birth defects would depend on the specific areas of the chromosomes that were lost or duplicated in the chromosomes that are translocated and what specific genes are located at these sites. For many unbalanced rearrangements (translocations) it is not possible to predict what abnormalities to expect; for others the medical literature may provide information.

I cannot provide any additional information than from what the genetics professional most likely gave you. You might consider contacting the Chromosome Deletion Outreach support group - they may be helpful. In looking at their website, (listed below) in the Registered Disorders heading, under translocations - I found two cases for 7 and 12 translocations listed - one is balanced the other unbalanced. These cases come from all over the world. Members of the support group can register and list the chromosome finding of their child. Perhaps they can provide you with additional help.

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